String Array quickie

[Bradley Olson]

I'm looking for smaller-scale dynamic-string allocation.

Arrays of strings are just contiguous arrays of pb string handles, right?

local S$(), pS as string ptr
dim S$(14)
pS = varptr( S$) 'NOT STRPTR!
@pS[1] = "This is string 1."
@pS[2] = "This is string 2."
@pS[3] = "This is string 3."
'etc...

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[Semen Matusovski]

Should be pS = VarPtr(S(0))

   #Compile Exe
   %n = 100000
   Function PbMain
     Local s() As String, pS As String Ptr, i As Long

     Dim S(%n)
     pS = VarPtr(S(0))

     For i = 0 To %n
        @pS[i] = "This is string" + Str$(i)
     Next
     
     ' Test
     For i = 0 To %n
        If S(i) <> "This is string" + Str$(i) Then MsgBox "Oh"
     Next
     
     MsgBox "Finish"
     
  End Function

If you want to imitate, how PB keeps strings (without Dim S() As String), I think that it's possible and more or less easy, something like this
(not optimal code, just idea only)

   #Compile Exe
   %n = 10 ' no. of elements
   %sz = 1000000 ' maximum size (total)
   
   Function PbMain
     Local s As String, tmp As Asciiz * 81, pS As String Ptr
     Dim i As Long, js As Long, k As Long, kk As Long
     
     s = Space$(%sz)
     
     pS = StrPtr(S)
     js = 4 * %n
     For i = 0 To (%n - 1)
        tmp = "This is string" + Str$(i): kk = Len(Tmp)
        
        k = 4 * (Fix(kk / 4) + 2)
        Mid$(s, 4 * i + 1, 4) = Mkl$(ps + js + 4)
        Mid$(s$, js + 1, kk + 5) = Mkl$(kk) + Tmp + Chr$(0)
        js = js + k
     Next
     
     For i = 0 To (%n - 1)
        If @pS[i] <> "This is string" + Str$(i) Then MsgBox Str$(Len(@ps[i]))
     Next

     MsgBox "Finish"

  End Function

[This message has been edited by Semen Matusovski (edited December 12, 2000).]

[Charles Dietz]

Semen,

In your simulation of PB string storage, why are the strings stored
on 4 byte boundaries?

It seems more efficient to simply let k = kk + 5,
rather than k = 4 * (Fix(kk / 4) + 2).

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[Lance Edmonds]

DWORD alignment is the most efficient way of storing most kinds of data in Win32, as the compiled code can be optimized for memory access in this way.

For example, making fixed-length & ASCIIZ string and string members of UDT's a multiple of 4 bytes is the most efficient, as is the internal alignment of a UDT structure too.


------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>